alpar@906: /* -*- C++ -*-
alpar@921:  * src/lemon/bfs.h - Part of LEMON, a generic C++ optimization library
alpar@906:  *
alpar@906:  * Copyright (C) 2004 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
alpar@906:  * (Egervary Combinatorial Optimization Research Group, EGRES).
alpar@906:  *
alpar@906:  * Permission to use, modify and distribute this software is granted
alpar@906:  * provided that this copyright notice appears in all copies. For
alpar@906:  * precise terms see the accompanying LICENSE file.
alpar@906:  *
alpar@906:  * This software is provided "AS IS" with no warranty of any kind,
alpar@906:  * express or implied, and with no claim as to its suitability for any
alpar@906:  * purpose.
alpar@906:  *
alpar@906:  */
alpar@906: 
alpar@921: #ifndef LEMON_BFS_H
alpar@921: #define LEMON_BFS_H
alpar@774: 
alpar@774: ///\ingroup flowalgs
alpar@774: ///\file
alpar@774: ///\brief Bfs algorithm.
alpar@774: ///
alpar@774: ///\todo Revise Manual.
alpar@774: 
alpar@921: #include <lemon/bin_heap.h>
alpar@921: #include <lemon/invalid.h>
klao@977: #include <lemon/graph_utils.h>
alpar@774: 
alpar@921: namespace lemon {
alpar@774: 
alpar@774: /// \addtogroup flowalgs
alpar@774: /// @{
alpar@774: 
alpar@781:   ///%BFS algorithm class.
alpar@774: 
alpar@781:   ///This class provides an efficient implementation of %BFS algorithm.
alpar@781:   ///\param GR The graph type the algorithm runs on.
alpar@781:   ///This class does the same as Dijkstra does with constant 1 edge length,
alpar@781:   ///but it is faster.
alpar@774:   ///
alpar@781:   ///\author Alpar Juttner
alpar@774: 
alpar@774: #ifdef DOXYGEN
alpar@774:   template <typename GR>
alpar@774: #else
alpar@774:   template <typename GR>
alpar@774: #endif
alpar@774:   class Bfs{
alpar@774:   public:
alpar@774:     ///The type of the underlying graph.
alpar@774:     typedef GR Graph;
alpar@911:     ///\e
alpar@774:     typedef typename Graph::Node Node;
alpar@911:     ///\e
alpar@774:     typedef typename Graph::NodeIt NodeIt;
alpar@911:     ///\e
alpar@774:     typedef typename Graph::Edge Edge;
alpar@911:     ///\e
alpar@774:     typedef typename Graph::OutEdgeIt OutEdgeIt;
alpar@774:     
alpar@774:     ///\brief The type of the map that stores the last
alpar@774:     ///edges of the shortest paths.
alpar@774:     typedef typename Graph::template NodeMap<Edge> PredMap;
alpar@774:     ///\brief The type of the map that stores the last but one
alpar@774:     ///nodes of the shortest paths.
alpar@774:     typedef typename Graph::template NodeMap<Node> PredNodeMap;
alpar@774:     ///The type of the map that stores the dists of the nodes.
alpar@774:     typedef typename Graph::template NodeMap<int> DistMap;
alpar@774: 
alpar@774:   private:
alpar@802:     /// Pointer to the underlying graph.
alpar@774:     const Graph *G;
alpar@802:     ///Pointer to the map of predecessors edges.
alpar@774:     PredMap *predecessor;
alpar@802:     ///Indicates if \ref predecessor is locally allocated (\c true) or not.
alpar@774:     bool local_predecessor;
alpar@802:     ///Pointer to the map of predecessors nodes.
alpar@774:     PredNodeMap *pred_node;
alpar@802:     ///Indicates if \ref pred_node is locally allocated (\c true) or not.
alpar@774:     bool local_pred_node;
alpar@802:     ///Pointer to the map of distances.
alpar@774:     DistMap *distance;
alpar@802:     ///Indicates if \ref distance is locally allocated (\c true) or not.
alpar@774:     bool local_distance;
alpar@774: 
alpar@802:     ///The source node of the last execution.
alpar@774:     Node source;
alpar@774: 
alpar@774: 
alpar@781:     ///Initializes the maps.
alpar@774:     void init_maps() 
alpar@774:     {
alpar@774:       if(!predecessor) {
alpar@774: 	local_predecessor = true;
alpar@774: 	predecessor = new PredMap(*G);
alpar@774:       }
alpar@774:       if(!pred_node) {
alpar@774: 	local_pred_node = true;
alpar@774: 	pred_node = new PredNodeMap(*G);
alpar@774:       }
alpar@774:       if(!distance) {
alpar@774: 	local_distance = true;
alpar@774: 	distance = new DistMap(*G);
alpar@774:       }
alpar@774:     }
alpar@774:     
alpar@774:   public :    
alpar@802:     ///Constructor.
alpar@802:     
alpar@802:     ///\param _G the graph the algorithm will run on.
alpar@911:     ///
alpar@774:     Bfs(const Graph& _G) :
alpar@774:       G(&_G),
alpar@774:       predecessor(NULL), local_predecessor(false),
alpar@774:       pred_node(NULL), local_pred_node(false),
alpar@774:       distance(NULL), local_distance(false)
alpar@774:     { }
alpar@774:     
alpar@802:     ///Destructor.
alpar@774:     ~Bfs() 
alpar@774:     {
alpar@774:       if(local_predecessor) delete predecessor;
alpar@774:       if(local_pred_node) delete pred_node;
alpar@774:       if(local_distance) delete distance;
alpar@774:     }
alpar@774: 
alpar@774:     ///Sets the map storing the predecessor edges.
alpar@774: 
alpar@774:     ///Sets the map storing the predecessor edges.
alpar@774:     ///If you don't use this function before calling \ref run(),
alpar@774:     ///it will allocate one. The destuctor deallocates this
alpar@774:     ///automatically allocated map, of course.
alpar@774:     ///\return <tt> (*this) </tt>
alpar@774:     Bfs &setPredMap(PredMap &m) 
alpar@774:     {
alpar@774:       if(local_predecessor) {
alpar@774: 	delete predecessor;
alpar@774: 	local_predecessor=false;
alpar@774:       }
alpar@774:       predecessor = &m;
alpar@774:       return *this;
alpar@774:     }
alpar@774: 
alpar@774:     ///Sets the map storing the predecessor nodes.
alpar@774: 
alpar@774:     ///Sets the map storing the predecessor nodes.
alpar@774:     ///If you don't use this function before calling \ref run(),
alpar@774:     ///it will allocate one. The destuctor deallocates this
alpar@774:     ///automatically allocated map, of course.
alpar@774:     ///\return <tt> (*this) </tt>
alpar@774:     Bfs &setPredNodeMap(PredNodeMap &m) 
alpar@774:     {
alpar@774:       if(local_pred_node) {
alpar@774: 	delete pred_node;
alpar@774: 	local_pred_node=false;
alpar@774:       }
alpar@774:       pred_node = &m;
alpar@774:       return *this;
alpar@774:     }
alpar@774: 
alpar@774:     ///Sets the map storing the distances calculated by the algorithm.
alpar@774: 
alpar@774:     ///Sets the map storing the distances calculated by the algorithm.
alpar@774:     ///If you don't use this function before calling \ref run(),
alpar@774:     ///it will allocate one. The destuctor deallocates this
alpar@774:     ///automatically allocated map, of course.
alpar@774:     ///\return <tt> (*this) </tt>
alpar@774:     Bfs &setDistMap(DistMap &m) 
alpar@774:     {
alpar@774:       if(local_distance) {
alpar@774: 	delete distance;
alpar@774: 	local_distance=false;
alpar@774:       }
alpar@774:       distance = &m;
alpar@774:       return *this;
alpar@774:     }
alpar@774:     
alpar@774:   ///Runs %BFS algorithm from node \c s.
alpar@774: 
alpar@774:   ///This method runs the %BFS algorithm from a root node \c s
alpar@774:   ///in order to
alpar@781:   ///compute a
alpar@774:   ///shortest path to each node. The algorithm computes
alpar@781:   ///- The %BFS tree.
alpar@774:   ///- The distance of each node from the root.
alpar@774:  
alpar@774:     void run(Node s) {
alpar@774:       
alpar@774:       init_maps();
alpar@774:       
alpar@774:       source = s;
alpar@774:       
alpar@774:       for ( NodeIt u(*G) ; u!=INVALID ; ++u ) {
alpar@774: 	predecessor->set(u,INVALID);
alpar@774: 	pred_node->set(u,INVALID);
alpar@774:       }
alpar@774:       
klao@946:       int N = countNodes(*G);
alpar@774:       std::vector<typename Graph::Node> Q(N);
alpar@774:       int Qh=0;
alpar@774:       int Qt=0;
alpar@774:       
alpar@774:       Q[Qh++]=source;
alpar@774:       distance->set(s, 0);
alpar@774:       do {
alpar@774: 	Node m;
alpar@774: 	Node n=Q[Qt++];
alpar@774: 	int d= (*distance)[n]+1;
alpar@774: 	
alpar@774: 	for(OutEdgeIt e(*G,n);e!=INVALID;++e)
alpar@986: 	  if((m=G->target(e))!=s && (*predecessor)[m]==INVALID) {
alpar@774: 	    Q[Qh++]=m;
alpar@774: 	    predecessor->set(m,e);
alpar@774: 	    pred_node->set(m,n);
alpar@774: 	    distance->set(m,d);
alpar@774: 	  }
alpar@774:       } while(Qt!=Qh);
alpar@774:     }
alpar@774:     
alpar@774:     ///The distance of a node from the root.
alpar@774: 
alpar@774:     ///Returns the distance of a node from the root.
alpar@774:     ///\pre \ref run() must be called before using this function.
alpar@774:     ///\warning If node \c v in unreachable from the root the return value
alpar@774:     ///of this funcion is undefined.
alpar@774:     int dist(Node v) const { return (*distance)[v]; }
alpar@774: 
alpar@781:     ///Returns the 'previous edge' of the %BFS path tree.
alpar@774: 
alpar@781:     ///For a node \c v it returns the 'previous edge' of the %BFS tree,
alpar@781:     ///i.e. it returns the last edge of a shortest path from the root to \c
alpar@774:     ///v. It is \ref INVALID
alpar@774:     ///if \c v is unreachable from the root or if \c v=s. The
alpar@781:     ///%BFS tree used here is equal to the %BFS tree used in
alpar@774:     ///\ref predNode(Node v).  \pre \ref run() must be called before using
alpar@774:     ///this function.
alpar@774:     Edge pred(Node v) const { return (*predecessor)[v]; }
alpar@774: 
alpar@781:     ///Returns the 'previous node' of the %BFS tree.
alpar@774: 
alpar@781:     ///For a node \c v it returns the 'previous node' on the %BFS tree,
alpar@774:     ///i.e. it returns the last but one node from a shortest path from the
alpar@774:     ///root to \c /v. It is INVALID if \c v is unreachable from the root or if
alpar@781:     ///\c v=s. The shortest path tree used here is equal to the %BFS
alpar@774:     ///tree used in \ref pred(Node v).  \pre \ref run() must be called before
alpar@774:     ///using this function.
alpar@774:     Node predNode(Node v) const { return (*pred_node)[v]; }
alpar@774:     
alpar@774:     ///Returns a reference to the NodeMap of distances.
alpar@774:     
alpar@774:     ///Returns a reference to the NodeMap of distances. \pre \ref run() must
alpar@774:     ///be called before using this function.
alpar@774:     const DistMap &distMap() const { return *distance;}
alpar@774:  
alpar@781:     ///Returns a reference to the %BFS tree map.
alpar@774: 
alpar@774:     ///Returns a reference to the NodeMap of the edges of the
alpar@781:     ///%BFS tree.
alpar@774:     ///\pre \ref run() must be called before using this function.
alpar@774:     const PredMap &predMap() const { return *predecessor;}
alpar@774:  
alpar@781:     ///Returns a reference to the map of last but one nodes of shortest paths.
alpar@774: 
alpar@781:     ///Returns a reference to the NodeMap of the last but one nodes on the
alpar@781:     ///%BFS tree.
alpar@774:     ///\pre \ref run() must be called before using this function.
alpar@774:     const PredNodeMap &predNodeMap() const { return *pred_node;}
alpar@774: 
alpar@774:     ///Checks if a node is reachable from the root.
alpar@774: 
alpar@774:     ///Returns \c true if \c v is reachable from the root.
alpar@802:     ///\note The root node is reported to be reached!
alpar@774:     ///
alpar@774:     ///\pre \ref run() must be called before using this function.
alpar@774:     ///
alpar@780:     bool reached(Node v) { return v==source || (*predecessor)[v]!=INVALID; }
alpar@774:     
alpar@774:   };
alpar@774:   
alpar@774: /// @}
alpar@774:   
alpar@921: } //END OF NAMESPACE LEMON
alpar@774: 
alpar@774: #endif
alpar@774: 
alpar@774: